From b58d4bef1070c6ca57008756d86f79a687d2bbea Mon Sep 17 00:00:00 2001
From: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Date: Mon, 23 Oct 2017 18:32:09 +0300
Subject: [PATCH] drm/i915: Disable lazy PPGTT page table optimization for vGPU
Git-commit: b58d4bef1070c6ca57008756d86f79a687d2bbea
Patch-mainline: v4.15-rc1
References: FATE#322643 bsc#1055900
No-fix: 22a8a4fc93b14b5a8cfc785edbdc6f7bd98bffb6

When running under virtualization (vGPU active), we must disable
the lazy PPGTT page table initialization optimization introduced by
commit 14826673247e ("drm/i915: Only initialize partially filled
pagetables").

We must do this because GVT-g makes unduly assumptions about guest
behaviour, which this optimization breaks. This results in following
looking errors in the host:

ERROR gvt: guest page write error -22, gfn 0x7ada8, pa 0x7ada89a8, var 0x6, len 1

The real fix is to not to depend on i915 driver behaviour, but instead
either rely on only the contracts that i915 has with the hardware, or
add some paravirtualization. While the real fix is en route, it won't
be finished in time for 4.15, so the best option is to disable the
optimization for now when vGPU is active to avoid breaking 4.15 guests
in existing VM environments.

Fixes: 14826673247e ("drm/i915: Only initialize partially filled pagetables")
Suggested-by: Xiaolin Zhang <xiaolin.zhang@intel.com>
Signed-off-by: Xiaolin Zhang <xiaolin.zhang@intel.com>
[joonas: Rewrote the commit message and added tags.]
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171023153209.10527-1-joonas.lahtinen@linux.intel.com
(cherry picked from commit 22a8a4fc93b14b5a8cfc785edbdc6f7bd98bffb6)

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_gtt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1337,7 +1337,7 @@ static int gen8_ppgtt_alloc_pd(struct i9
 			if (IS_ERR(pt))
 				goto unwind;
 
-			if (count < GEN8_PTES)
+			if (count < GEN8_PTES || intel_vgpu_active(vm->i915))
 				gen8_initialize_pt(vm, pt);
 
 			gen8_ppgtt_set_pde(vm, pd, pt, pde);